Mental fabrications/formations are in several suttas listed as being feelings & perceptions;

Perceptions & feelings are mental; these are things tied up with the mind. That's why perceptions & feelings are mental fabrications. - MN44 and SN41.6

but why are perceptions and feelings and mental fabrications listed as two different categories among the five aggregates? Might this be for practical reasons of discerning processes at various times rather than describing objectively what a human is and therefore not contradictory, or do I just need some Dhamma 101?

The three terms—kayasȧkhāra, vacı̄saṅkhāra, cittasȧkhara—are in Pāli identical with those that make up the saṅkhāra factor of dependent origination (as at 12:2; see II, n. 7), but in this context the purport is different, as the following discussion will show. Here, in the compounds kāyasaṅkhāra and cittasaṅkhāra, saṅkhāra clearly has a passive sense: what is formed or generated (sȧkharı̄yati) in dependence on the body or the mind. In the case of vacı̄saṅkhāra the sense is active: what generates (sȧkharoti) speech

So the context of sankhara is important since it carries both the passive sense and the active sense. The 'Volitional formation' in the Five Aggregates refer to the active sense of the term. (Refer to http://en.wikipedia.org/wiki/Sankhara for passive and active definitions)

richard_rca wrote:Mental fabrications/formations are in several suttas listed as being feelings & perceptions;

Perceptions & feelings are mental; these are things tied up with the mind. That's why perceptions & feelings are mental fabrications. - MN44 and SN41.6

but why are perceptions and feelings and mental fabrications listed as two different categories among the five aggregates? Might this be for practical reasons of discerning processes at various times rather than describing objectively what a human is and therefore not contradictory, or do I just need some Dhamma 101?

Yes, for practical reasons and the terms are only nominal differentiation, nothing inheres in the terms that might be "objective". "Fabrications" may be equated with "experience". "Fabrications" may be further differentiated as "mental", "verbal" and "bodily fabrications" and/or differentiated as "the 5 aggregates". The earlier and the more 'detached' fabrications are noted the less differentiated experience appears i.e. only "fabrications" of undetermined type and origine can be noted in early stages of dependent origination. The later and the more 'grasping' (conciousness based) fabrications are noted the more differentiated these appear. E.g. what is mere undetermined fabrication in the beginning transforms into full-fledged feeling or perception later being conditioned by contact (phassa) and attention which are the nutriment for determining consciousness. It is important to note the interdependency of this process, since there are neither feeling nor perception without conscious contribution. So consciousness "makes up" what consciousness cognizes nurtured by contact and attention.

He deals with the Culavedalla Sutta quote which you cite in your original post. He takes sankhara to mean "determinant", or "a thing from which some other thing is inseparable - in other words, a necessary condition". So perceptions and feelings are necessary conditions of any mental phenomenon. No perceptions or feelings = no mentality.

This obviously departs from Bikkhu Bodhi's (and nearly everybody else's!) more context-bound definition of sankhara, but reading through Notes on Dhamma it looks as if he is able to use this definition consistently in different contexts.

ground wrote:Yes, for practical reasons and the terms are only nominal differentiation, nothing inheres in the terms that might be "objective". "Fabrications" may be equated with "experience". "Fabrications" may be further differentiated as "mental", "verbal" and "bodily fabrications" and/or differentiated as "the 5 aggregates". The earlier and the more 'detached' fabrications are noted the less differentiated experience appears i.e. only "fabrications" of undetermined type and origine can be noted in early stages of dependent origination. The later and the more 'grasping' (conciousness based) fabrications are noted the more differentiated these appear. E.g. what is mere undetermined fabrication in the beginning transforms into full-fledged feeling or perception later being conditioned by contact (phassa) and attention which are the nutriment for determining consciousness. It is important to note the interdependency of this process, since there are neither feeling nor perception without conscious contribution. So consciousness "makes up" what consciousness cognizes nurtured by contact and attention.

That sounds like papanca, ground.

MN 44 explains these sankhara are simply the 'conditioner' of the other. For example, it says 'based on what one thinks, one breaks out into speech. Thus thinking is the verbal conditioner (vaci sankhara)'.

You may also have a look at Buddhadasa's A Manual For Serious Beginners Step 3 & Step 7 and also Thanissaro's Shape of Suffering.

ground wrote:Yes, for practical reasons and the terms are only nominal differentiation, nothing inheres in the terms that might be "objective". "Fabrications" may be equated with "experience". "Fabrications" may be further differentiated as "mental", "verbal" and "bodily fabrications" and/or differentiated as "the 5 aggregates". The earlier and the more 'detached' fabrications are noted the less differentiated experience appears i.e. only "fabrications" of undetermined type and origine can be noted in early stages of dependent origination. The later and the more 'grasping' (conciousness based) fabrications are noted the more differentiated these appear. E.g. what is mere undetermined fabrication in the beginning transforms into full-fledged feeling or perception later being conditioned by contact (phassa) and attention which are the nutriment for determining consciousness. It is important to note the interdependency of this process, since there are neither feeling nor perception without conscious contribution. So consciousness "makes up" what consciousness cognizes nurtured by contact and attention.

That sounds like papanca, ground.

Papanca may be the nature of all verbal expressions. The opposite may be silence - from a hearer's perspective. It has been said that "consciousness 'makes up' what conciousness cognizes" therefore the said (which "sounds like papanca" in the readers sphere) of course is covered by this statement too and so is the reader's cognition. That does however not negate what is being expressed considering that the words by means of which expression occurs are not that what is being expressed. Therefore the ideas arising upon reading are not that what is being expressed either.

This again is willingly acknowledged to may sound like papanca. But did you get the message nevertheless?

'Citta' is mind, in terms of defilement & non-defilement. 'Citta' is described in the Satipattana Sutta & in the Dhammapada.

And how does a monk remain focused on the mind in & of itself? There is the case where a monk, when the mind has passion, discerns that the mind has passion. When the mind is without passion, he discerns that the mind is without passion. When the mind has aversion, he discerns that the mind has aversion. When the mind is without aversion, he discerns that the mind is without aversion. When the mind has delusion, he discerns that the mind has delusion. When the mind is without delusion, he discerns that the mind is without delusion.

MN 10

33. Just as a fletcher straightens an arrow shaft, even so the discerning man straightens his mind — so fickle and unsteady, so difficult to guard.

34. As a fish when pulled out of water and cast on land throbs and quivers, even so is this mind agitated. Hence should one abandon the realm of Mara.

35. Wonderful, indeed, it is to subdue the mind, so difficult to subdue, ever swift, and seizing whatever it desires. A tamed mind brings happiness.

What one feels, one perceives (labels in the mind). What one perceives, one thinks about. What one thinks about, one objectifies. Based on what a person objectifies, the perceptions & categories of objectification assail him/her with regard to past, present, & future.